Lubricity is a quantitative term describing the ability of fluid to affect friction between surfaces that are in relative motion under load and to assess the wear to the metal surfaces. Texas OilTech Laboratories Inc. offers a sophisticated and well equipped laboratory for the evaluation of lubricity by one of several available techniques.

 

Diesel Fuel Lubricity
Diesel fuel lubricity is an important fuel oil characteristic, especially with the advent of lower sulfur diesel fuels in the 1990s. Presently, the specification for low-sulfur diesel fuel is set at 0.5% mass sulfur. This has made a significant improvement in our environment. However, the refinery processing techniques that reduce the sulfur content of a diesel fuel may also remove certain polar and aromatic compounds that give the fuel its lubricity properties.


Lubricity of a diesel fuel describes the ability of the fluid to affect the friction between moving metal surfaces. A lack of suitable lubricity can result in shortened life of engine components such as fuel injection pumps and injectors. Therefore, certain additive packages must be introduced into a low-sulfur diesel fuel to compensate for those hydrocarbons that provided the fuels natural lubricity.


The regulations for low-sulfur diesel fuels are expected to be even tighter by the year 2006, when ultra-low-level-sulfur diesel requirements will be introduced. Work is now underway to enable fuel producers and users to meet those requirements. One of the challenges is to have laboratory instrumentation that can be used to measure and predict a fuels lubricity performance when carrying low concentrations of additives.

HFRR Tester - High-Frequency Reciprocating Rig
ASTM D 6079 is the standardized procedure for evaluating the lubricity of a diesel fuel using a high-frequency reciprocating rig (HFRR). It is applicable to middle distillate fuels such as No. 1D, No. 2D, Low-sulfur No. 1D and No. 2D, and other similar petroleum-based fuels that are used in diesel engines. Texas OilTech Laboratories Inc. has the PCS Instrument Model HFR2 High Frequency Reciprocating Rig, plus a high-resolution microscope and digital camera, which provide the most advanced and accurate test for lubricity in fuels. This test is designed to evaluate boundary lubrication properties of a diesel fuel. Two test temperatures can be used: 25 °C and 60 °C.


BOCLE and SLBOCLE Tester
Ball-on-Cylinder Lubricity Evaluator
Scuffing Load Ball-on-Cylinder Lubricity Evaluator


The SLBOCLE test, ASTM D 6078, is also used to evaluate diesel fuel lubricity. Texas OilTech Laboratories, Inc. has the Model BOC-2000 Lubricity Evaluator (InterAv, Inc.). It is applicable to the same middle distillate fuels as the HFRR test and provides an alternate assessment of boundary lubrication.


SLBOCLE test results have been shown to provide an indication of diesel injection system pump component problems due to wear. This has been demonstrated in pump rig tests for different fuel/hardware combinations, where boundary lubrication was believed to be the contributing mechanism.


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References
1. ASTM D 6079 Standard Test Method for Evaluating Lubricity of Diesel Fuels by the High Frequency Reciprocating Rig (HFRR)
2. ASTM D 5001 Standard Test Method for Measurement of Lubricity of Aviation Turbine Fuels by the Ball-on-Cylinder Lubricity Evaluator (BOCLE)
3. ASTM D 6078 Standard Test Method for Evaluating Lubricity of Diesel Fuels by the Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLBOCLE)
• Procedure A: Incremental Load
• Procedure B: Single-Load Test
4. ASTM D 2625 Test Method for Endurance (Wear) Life and Load Carrying Film Lubricants (Falex Pin and Vee Method)
5. ASTM D 2266 Test Method for Wear Preventive Characteristics of Lubricating Fluid (Four-Ball Method)
6. ASTM D 2782 Test Method for Measurement of Extreme-Pressure Properties of Lubricating Fluids (Timken Method)